Abundance of Cereal Aphids (Homoptera: Aphididae) and Their Predators in Spring Wheat-Alfalfa Intercrops Under Different Crop Management Intensities

Natural infestations of cereal aphids and abundance of their predators were compared from 1990 through 1993 among plots of intercropped spring wheat and alfalfa grown under high, intermediate, or low crop management intensity (CMI). CMI treatments differed in the amount of nitrogen fertilizer applied and herbicide used and in the rigor of tillage operations. Cereal aphids (primarily Rhopalosiphum padi, Sitobion avenae, and Schizaphis graminum) collectively infested a mean of 0 to 5.9 of 15 wheat tillers sam­pled per plot on various dates from 1990 through 1993, but aphid infestation did not vary by CM!. Seven taxa of aphid predators predominated: Nabis spp., Chrysoperla spp., Coleomegilla maculata, Hippodamia convergens, H. tredecimpunctata tibialis, H. parenthesis, and Coccinella septempunctata. Coccinella transversoguttata richardsoni, a species in decline in eastern South Dakota, was not collected. Nabids were generally the most abundant predatory taxon. In 1992, coccinellid adults were more abundant in high than low CMI plots. In 1993, H. tredecimpunctata tibialis adults were significantly more abundant in high CMI plots on the first three sampling dates but became more abundant in the low and intermediate CMI plots by the fifth sampling date. Regressions between the number of aphid-infested tillers and abundance of some predator taxa were significant in 1990, 1991, and 1992. In 1990, most regressions showed that counts of predators (except Chrysoperla spp. adults) were inversely proportional to aphid infestation levels, whereas significant regressions in 1991 and 1992 showed that the abundances of predators were weakly proportional to aphid infestation levels. Adjusted r2 values for all significant regressions ranged from 0.07 to 0.27. Relationships between crop management, cereal aphid infestation, and aphidophagous predators are discussed

The Electrochemical Characterization of a Platinum Cyclooctadiene Complex as a Guest Molecule in the Presence of ß-Cyclodextrin

The equilibrium constants for the complexation of the dichloroplatinum- cycloocta-1,5-diene complex with p-cyclodextrin in N,N-dimethyl- formamide was determined using electrochemical cyclic voltammetry. The constants for both the oxidized and reduced forms of the platinum compound were determined. Model redox experiments were conducted with ferrocene and 1,1 ’-dimethylferrocene before the platinum compound was studied in order to establish parameters for the experimental method. Also determined was the ratio of the diffusion constants of the guest molecule with and without being complexed with cyclodextrin. In addition to the platinum complex being electrochemically characterized as a guest of cyclodextrin, circular dichroism studies were conducted as well. The results contribute to the understanding of the inclusion-expulsion equilibrium mechanism for the guest-host pair. The results can potentially provide insight for applying inclusion compound chemistry for analytical chemical separations and controlled oxidation-reduction chemistry in specific molecular environments

Application of Barton Esters in Polymer Modification.

Esters of N-hydroxypyridine-2-thione, known as Barton esters, dissociate homolytically upon exposure to heat or light generating chain initiating acyloxy radicals and pyridine sulfide radicals that lead to 2,2\u27-dipyridyl disulfide. The dominant mode of Barton ester consumption is chain transfer, yielding pyridinesulfide end groups and acyloxy radicals. Thermolysis (80°C) or photolysis (25°C) of Barton esters initiated polymerization of styrene. The polymerization rate was found to be independent of Barton ester concentration. Chain transfer to initiator controls molecular weight; the chain transfer constants for phenyl Barton ester in styrene and acrylamide are 0.96 and 0.08 respectively. Polymer end-groups were identified as an ester group and a pyridinesulfide group, which was quaternized with iodomethane (88% yield). Incorporation of Barton esters into the side groups of polymer chains facilitated the synthesis of graft copolymers; the asymmetric dissociation of the initiating moiety limits concomitant homopolymerization to under 8%. Grafting to Barton esterified poly(methacylate) backbones was accompanied by chain cleavage. Introduction of a phenyl linkage via poly(4-vinyl benzoate) eliminated this side reaction. Poly(arylene ether sulfone) elaborated by carboxylation (0.15 to 1.0 carboxyl groups per repeat unit) was Barton esterified in 95% yield, and styrene was grafted using photolytic conditions. Intramolecular chain transfer limited graft length from 10 to a maximum of 180 repeat units. Grafting of styrene to Barton esterified carboxymethyl cellulose was accompanied by backbone chain cleavage. Elaboration of hydroxypropyl cellulose with 1-oxa-2-oxo-3-thiaindolizinium chloride yielded a polymeric initiator on a stable cellulosic backbone. Graft copolymers to each of the polymeric initiators were formed from the following monomers: styrene, methyl methacrylate, 4-vinylpyridine, and acrylamide. Homolytic cleavage of phenyl Barton ester in the presence of styrene and the tetramethylpiperidinyloxy (TEMPO) radical yields a TEMPO adduct (23%), which effects controlled radical polymerization of styrene. Extension of this synthesis to Barton esterified polymers yields substrates, which allow controlled graft copolymerization. The resultant ester linkage between backbone and graft allows the selective removal of the grafts for independent analysis. Depending upon polymerization times, grafts of polystyrene to both poly(arylene ether sulfone) and hydroxypropyl cellulose with number average molecular weights ranging from 28,000 to 89,000 can be achieved

Methods for Agricultural Policy Analysis: An Overview

This article summarizes the articles that have been presented at the Workshop on Methods for Agricultural Policy Analysis held at UP Los Baños on August 13-14, 1985. It has four parts: the farm production/productivity change, the food consumption, the rural/ agricultural households in imperfect market settings and the methodologies for combining partial and general equilibrium framework.economic/development modelling, computable general equilibrium (CGE), agriculture sector

Abundance of Cereal Aphids (Homoptera: Aphididae) and Their Predators in Spring Wheat-Alfalfa Intercrops Under Different Crop Management Intensities

Natural infestations of cereal aphids and abundance of their predators were compared from 1990 through 1993 among plots of intercropped spring wheat and alfalfa grown under high, intermediate, or low crop management intensity (CMI). CMI treatments differed in the amount of nitrogen fertilizer applied and herbicide used and in the rigor of tillage operations. Cereal aphids (primarily Rhopalosiphum padi, Sitobion avenae, and Schizaphis graminum) collectively infested a mean of 0 to 5.9 of 15 wheat tillers sam­pled per plot on various dates from 1990 through 1993, but aphid infestation did not vary by CM!. Seven taxa of aphid predators predominated: Nabis spp., Chrysoperla spp., Coleomegilla maculata, Hippodamia convergens, H. tredecimpunctata tibialis, H. parenthesis, and Coccinella septempunctata. Coccinella transversoguttata richardsoni, a species in decline in eastern South Dakota, was not collected. Nabids were generally the most abundant predatory taxon. In 1992, coccinellid adults were more abundant in high than low CMI plots. In 1993, H. tredecimpunctata tibialis adults were significantly more abundant in high CMI plots on the first three sampling dates but became more abundant in the low and intermediate CMI plots by the fifth sampling date. Regressions between the number of aphid-infested tillers and abundance of some predator taxa were significant in 1990, 1991, and 1992. In 1990, most regressions showed that counts of predators (except Chrysoperla spp. adults) were inversely proportional to aphid infestation levels, whereas significant regressions in 1991 and 1992 showed that the abundances of predators were weakly proportional to aphid infestation levels. Adjusted r2 values for all significant regressions ranged from 0.07 to 0.27. Relationships between crop management, cereal aphid infestation, and aphidophagous predators are discussed

A systematic review of interventions for promoting active transportation to school

<p>Abstract</p> <p>Background</p> <p>Active transportation to school is an important contributor to the total physical activity of children and adolescents. However, active school travel has declined over time, and interventions are needed to reverse this trend. The purpose of this paper is to review intervention studies related to active school transportation to guide future intervention research.</p> <p>Methods</p> <p>A systematic review was conducted to identify intervention studies of active transportation to school published in the scientific literature through January 2010. Five electronic databases and a manual search were conducted. Detailed information was extracted, including a quantitative assessment comparing the effect sizes, and a qualitative assessment using an established evaluation tool.</p> <p>Results</p> <p>We identified 14 interventions that focused on active transportation to school. These interventions mainly focused on primary school children in the United States, Australia, and the United Kingdom. Almost all the interventions used quasi-experimental designs (10/14), and most of the interventions reported a small effect size on active transportation (6/14).</p> <p>Conclusion</p> <p>More research with higher quality study designs and measures should be conducted to further evaluate interventions and to determine the most successful strategies for increasing active transportation to school.</p

Association Between Physical Activity and Proximity to Physical Activity Resources Among Low-Income, Midlife Women

INTRODUCTION: The association between levels of physical activity and perceived and objectively measured proximity to physical activity resources is unclear. Clarification is important so that future programs can intervene upon the measure with the greatest association. We examined correlations between perceived and objectively measured proximity to physical activity resources and then examined associations between both measures of proximity and objectively measured physical activity. METHODS: Participants (n = 199) were underinsured women from three counties in southeastern North Carolina. Perceived proximity to physical activity resources (e.g., parks, gyms, schools) was measured using surveys. Objectively measured proximity included geographic information systems road network distance to the closest resource and existence of resources within 1- and 2-mile buffers surrounding participants' homes. To examine the association between proximity to resources and activity, the dependent variable in multiple linear regression models was the natural logarithm of accelerometer-measured moderate to vigorous physical activity in minutes per day. RESULTS: Pearson correlation coefficients for perceptions of distance and objectively measured distance to physical activity resources ranged from 0.40 (gyms, schools) to 0.54 (parks). Perceived distance to gyms and objective number of schools within 1-mile buffers were negatively associated with activity. No statistically significant relationships were found between activity and perceived or objectively measured proximity to parks. CONCLUSION: Results indicate the need for both individual and environmental intervention strategies to increase levels of physical activity among underinsured, midlife women. More work is needed to determine the most effective strategies

How do electronic carriers cross Si-bound alkyl monolayers?

Electron transport through Si-C bound alkyl chains, sandwiched between n-Si and Hg, is characterized by two distinct types of barriers, each dominating in a different voltage range. At low voltage, current depends strongly on temperature but not on molecular length, suggesting transport by thermionic emission over a barrier in the Si. At higher voltage, the current decreases exponentially with molecular length, suggesting tunneling through the molecules. The tunnel barrier is estimated, from transport and photoemission data, to be ~1.5 eV with a 0.25me effective mass.Comment: 13 pages, 3 figure

A comparison of alternative assays to measure DNA damage in stallion spermatozoa: TUNEL test versus ‘Nicoletti assay’

The aberrations of sperm DNA may cause various problems and have negative consequences on fertility. These influence embryonic development or might lead to early embryo loss. Sperm Chromatin Structure Assay (SCSA) is the flow cytometric method most often used for the detection of DNA lesions; however, some studies using that method reached confusing conclusions. The aim of this pilot study was to adjust and compare two alternative tests, namely the TUNEL test and the Nicoletti assay. The above-mentioned two flow cytometric methods capable of detecting the fragmented DNA of sperm were tested on 12 frozen-thawed stallion semen samples. The TUNEL test demonstrated much higher DNA fragmentation ratio than the Nicoletti assay (mean ± SD: 30.77 ± 13.03% vs. 1.93 ± 0.89%, respectively). A fluorescent microscopic check of the samples showed that TUNEL labelled the plasma membrane and the mitochondria in a nonspecific way, rather than detecting only the fragmented DNA, thus eventually resulting in a false positive sign. The Nicoletti assay is simpler, quicker and does not detect nonspecific binding; however, further analyses are required to determine its diagnostic value

The Relationship between Changes in Weight Status and Insulin Resistance in Youth

This study examined changes in insulin resistance (IR) in 120 youth over two years. IR was quantified via homeostatic model (HOMA-IR), and weight status changes were quantified via body mass index (BMI). When all participants were considered, the mean HOMA-IR and BMI increased 13.4% and 1.65 units, respectively. Change in BMI z-score and percent change in HOMA-IR were moderately associated (r = 0.39). Follow-up analyses were performed for the following weight groups: NN (normal at baseline and two years later), NO (normal to overweight), ON (overweight to normal), and OO (overweight at both points). The NO group had a greater change in HOMA-IR (+50%) compared to other groups: ON (−8%), NN (+2%), and OO (−0.1%) (P < .05). The association between changes in BMI z-score and HOMA-IR was r = 0.49 when only the NO and ON groups were included. These results reinforce the importance of preventing youth from becoming overweight to control IR